The potential impact of a 20mph limit on urban roads in Scotland

This Glasgow Centre for Population Health (GCPH) report presents three different potential scenarios – based on speed reductions observed in 20mph schemes in Bristol and central Edinburgh – and the resulting anticipated casualty reductions.

The report was developed in response to a call for evidence in the lead up to a forthcoming Scottish Parliament Member’s Bill proposing the introduction of a 20mph limit in urban settings across the country.

Scenario one is based on the average speed reductions seen since the introduction of a permanent 20mph scheme in Bristol. It predicts a 13.5% reduction in casualties across Scotland (755 fewer casualties), including five fewer fatalities, associated with savings of £39.9m per year.

Scenario two – described as a ‘middle estimate’ – is based on the average speed reductions observed in a 20mph pilot scheme in parts of Edinburgh. It anticipates a 9.5% reduction in casualties (531 fewer casualties), including three fewer fatalities and an annual saving of £27.1m.

The final scenario – a lower estimate – shows the reduction in overall casualties needed to save one life. The scenario is based on a 2.6% reduction in casualties (145 fewer casualties, including one fatality) and a saving of £7.8m per year.

The report says the successful introduction of a 20mph speed limit on urban roads in Scotland would be ‘impacted by different local contexts’ and the effectiveness of ‘complementary activities’ including communication, behaviour change campaigns, supportive policing and enforcement.